This invention relates to a construction for a filter in which a single or plurality of identical filter structures are connected to a pressure filter tank in a pressure filter apparatus in a plurality of stages to collect and discharge a large amount of filtrate.
In many cases, the filter material to be utilized in the conventional filter that effects a pressure surface filtering is prepared by pasting and fixing a filter material such as synthetic resin fiber including a cotton cloth to a frame member of the filter in a specific direction. The resulting filter material is used for the filtration operation, but when the filtration pressure is elevated, the filter material is deformed due to the filtering pressure of the untreated liquid which lowers the performance of or damages the filter apparatus. Therefore, the support frame of the filter cloth is designed and manufactured with a rigid material having a considerable margin for strength. It has been discovered that the filter pressure on both surfaces of the filter cloth can be cancelled out by the provision of a filter material including filter cloth on both of the surfaces centering around a core member with holes. There is no need to provide the extra strength of the support frame to the core member with holes. The core material can thus be molded with a relatively soft semi-hardening material, and a spacer effect for preventing the fusing of the filter cloth on both the surfaces can be provided to maintain the function of the filter liquid path.